Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 8 Sept 2026Clinical review pending
Saved on this device
Synopsis
Recognise renal infection, select oral or intravenous treatment from the clinical findings and investigate failure to improve before a drainable complication is missed.
Fever with flank pain, renal angle tenderness, rigors or vomiting suggests pyelonephritis, even when bladder symptoms are absent.
Send midstream urine for culture before antibiotics; assess observations, hydration, renal function and the possibility of obstruction at the same time.
Vomiting that prevents oral treatment, severe illness or an unsafe home situation favours hospital assessment and an intravenous regimen.
Key red flags
Physiological instability
Low blood pressure, altered consciousness, tachypnoea, oliguria or rising lactate requires a sepsis assessment and urgent senior involvement. A seemingly modest temperature does not make these findings benign.
Obstruction clues
Prior stones, severe colicky pain, a solitary functioning kidney, renal impairment or reduced urine output increases concern for an obstructed infected system. Infection plus obstruction requires urgent urological source control.
Investigation priorities
01
Midstream urine culture and susceptibilityFirst step
Establish a bacterial diagnosis and enable directed antibiotic review.
Management branches
Worked caseVomiting determines the initial route
A forty two year old woman has fever and right flank tenderness with repeated vomiting.
She is not pregnant, has no beta lactam allergy and has stable circulation, but cannot retain tablets. Creatinine is mildly above her documented baseline and she previously passed a ureteric stone, so urine culture and renal ultrasound are arranged during hospital assessment.
She starts ceftriaxone 2 g intravenously once daily, infused over at least thirty minutes, with hydration tailored to examination. Ultrasound shows no hydronephrosis. A calcium-containing infusion is not given simultaneously with ceftriaxone; shared lines are appropriately flushed between sequential adult administrations.
Oral treatmentManage a stable community presentation
The adult can take oral medicines and has no admission indication.
Key medicines
Ceftriaxone 2 g powder for intravenous infusionFor the admitted nonpregnant adult example, give 2 g intravenously every twenty four hours over at least thirty minutes; review intravenous need at forty eight hours.Do not administer with ceftriaxone or other cephalosporin hypersensitivity, or a history of severe hypersensitivity to another beta lactam. Never give a lidocaine-containing preparation intravenously. Do not mix with or administer simultaneously with calcium-containing intravenous fluids; adults can receive sequential treatment after line flushing. Monitor diarrhoea, rash and renal or neurological changes; combined severe liver and kidney dysfunction needs close review.
Cefalexin 500 mg oral capsulesFor an adult who can take oral treatment, use 500 mg twice or three times daily for seven to ten days; the worked switch completes ten total treatment days.Marked renal impairment requires dose adjustment using the selected product and pharmacy advice; do not continue a normal schedule into evolving severe kidney injury. Known cefalexin, excipient or cephalosporin-group allergy excludes this product; assess penicillin reactions carefully, with specialist selection after a severe reaction. Monitor severe skin reactions and antibiotic-associated diarrhoea. The selected capsule product has a usual adult maximum of 4 g daily, so higher guideline ranges must not be transferred uncritically to this formulation.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 8 Sept 2026; clinical approval remains outstanding.